U.S. patent application number 10/363965 was filed with the patent office on 2004-02-26 for method for producing a 3-d micro flow cell and a 3-d micro flow cell.
Invention is credited to Fuhr, Guenther, Howitz, Steffen.
Application Number | 20040038387 10/363965 |
Document ID | / |
Family ID | 26006966 |
Filed Date | 2004-02-26 |
United States Patent
Application |
20040038387 |
Kind Code |
A1 |
Howitz, Steffen ; et
al. |
February 26, 2004 |
Method for producing a 3-D micro flow cell and a 3-d micro flow
cell
Abstract
A 3D micro flow cell is fabricated by forming a first spacer on
a substrate to define the flow channel of the cell extending
between inlet and outlet openings. A second spacer, comprising a
pasty adhesive is applied outside the first spacer or in a groove
on the first spacer to seal the cell when the first substrate is
joined to a second substrate.
Inventors: |
Howitz, Steffen; (Dresden,
DE) ; Fuhr, Guenther; (Berlin, DE) |
Correspondence
Address: |
BAKER & BOTTS
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
|
Family ID: |
26006966 |
Appl. No.: |
10/363965 |
Filed: |
May 30, 2003 |
PCT Filed: |
September 3, 2001 |
PCT NO: |
PCT/DE01/03324 |
Current U.S.
Class: |
435/287.2 ;
438/1 |
Current CPC
Class: |
B81C 2201/019 20130101;
Y10T 29/49 20150115; B81B 2201/058 20130101; B81C 3/001 20130101;
Y10T 29/49002 20150115; B81C 1/00119 20130101; Y10T 436/11
20150115; G01N 27/44791 20130101 |
Class at
Publication: |
435/287.2 ;
438/1 |
International
Class: |
H01L 021/00; C12M
001/34 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 7, 2000 |
DE |
100 44 333.8 |
Feb 3, 2001 |
DE |
101 04 957.9 |
Claims
We claim:
1. A method of producing a 3D micro flow cell having a flow channel
arranged between an upper and a lower substrate and connected to
inlet and outlet fluid passages, wherein at least one of said
substrates includes electrode structure having external electrical
connections, comprising: applying a first spacer defining opposite
sides of said flow channel and permanently fixed to a first
substrate; applying non-compressible shims on at least one of said
substrates to define a separation of said substrates; applying a
second spacer comprising a pasty adhesive with uniform thickness to
one of said substrates, said second spacer being formed outside of
said flow channel; and positioning a second substrate over said
first substrate and joining said substrates by applying one of
force and heat to seal said flow channel.
2. A method as specified in claim 1 wherein said second spacer is
applied directly next to, parallel to and surrounding said first
spacer, and wherein prior to said positioning, said first spacer
has a thickness greater than a thickness of said first spacer.
3. A method as specified in claim 1, wherein a shallow groove is
provided extending along the length of said first spacer and
wherein said second spacer is applied in said groove.
4. A method as specified in claim 3 wherein said shallow groove is
applied by photolithographic methods.
5. A method as specified in claim 1 wherein said first spacer and
said shims are applied by screen printing and subsequently
cured.
6. A method as specified in claim 4 wherein said curing is
accomplished by one of heating and irradiation with light.
7. A method as specified in claim 1 wherein said first spacer and
said shims are applied by one, of photolithographic methods and
dispensing, and cured by tempering.
8. A method as specified in claim 7 wherein said first spacer and
shims are made of a photostructurable resist having a thickness
which defines the height of the flow channel.
9. A method as specified in claim 1 wherein said first spacer and
said shims are made of a prestructured film that is adhesive at
least on one side and affixed to a substrate.
10. A method as specified in claim 1 wherein a bond between said
upper substrate and said lower substrate is produced under the
action of pressure and one of heat and UV irradiation.
11. A method as specified in claim 1 wherein said second spacer is
formed from a material selected from an adhesive based on epoxy
resin and silicone rubber.
12. A 3d micro flow cell made by the method of any of claims 1 to
10.
13. A 3D micro flow cell, comprising: a flow channel arranged
between an upper and a lower substrate and connected to inlet and
outlet fluid passages, wherein at least one of said substrates
includes electrode structure having external electrical
connections; wherein: a first spacer is arranged on one of said
substrates defining said flow channel; shims made of a
substantially non-compressible material having a predetermined
thickness are permanently attached to one of said substrates to
define the spacing between said substrates and the height of said
flow channel; and said upper substrate is joined to said lower
substrate by a second spacer formed of a pasty, curable adhesive
layer, tightly sealing the flow channel.
14. A 3D micro flow cell in accordance with claim 13, wherein said
second spacer comprises a stripe along the outside of said first
spacer and said flow channel on both sides of said flow
channel.
15. A 3D micro flow cell in accordance with claim 14, wherein said
second spacer is provided in a shallow groove in a surface of said
first spacer.
16. A 3D micro flow cell in accordance with claim 13, wherein said
first spacer and said shims have an equal thickness between about
10 .mu.m and about 100 .mu.m.
17. A 3D micro flow cell in accordance with claim 13 wherein said
lower substrate is made of glass and has a thickness between about
250 .mu.m and 1000 .mu.m.
18. A 3D micro flow cell in accordance with claim 13 wherein said
upper substrate comprises a plastic film.
19. A 3D micro flow cell in accordance with claim 18 wherein said
upper substrate comprises a polymer film with a thickness between
about 170 .mu.m and 200 .mu.m.
20. A 3D micro flow cell in accordance with claim 13 wherein said
cell is optically transparent at least in the wavelength range from
250 nm to 450 nm in a region surrounding said flow channel.
21. A 3D micro flow cell in accordance with claim 13 wherein
metallic microelectrodes having a predetermined geometrical
relationship to one another are provided on one of said substrates
and wherein said upper substrate is mounted face down on said lower
substrate.
22. A 3D micro flow cell in accordance with claim 21 wherein
microelectrodes are provided on said upper substrate and are
connected to contact pads which are electrically connected to
external contacts on said lower substrate by one of conductive
adhesive, conductive rubber, or solder pads.
23. A 3D micro flow cell in accordance with claim 13 wherein said
electrode structure comprises microelectrodes made from a conductor
selected from platinum, gold, tantalum, titanium, aluminum, or
ITO.
24. A 3D micro flow cell in accordance with claim 22 wherein said
electrode structure is covered by an electrical insulating
material, except in the interior of said flow channel and on said
contact pads, and on contact supports.
25. A 3D micro flow cell in accordance with claim 13 wherein an
opaque mask is applied to the outside of said upper substrate in
such a manner that edges of said flow channel are covered, and a
central region of said flow channel is left clear.
26. A 3D micro flow cell in accordance with claim 25 wherein said
mask provides shielding against electromagnetic waves for suspended
cells.
27. A 3D micro flow cell in accordance with claim 26 wherein said
mask is metal.
28. A 3D micro flow cell in accordance with claim 27 wherein said
mask is a photolithographically structurable Cu or Al thin
film.
29. A 3D micro flow cell in accordance with claim 25 wherein said
mask is removable.
30. A 3D micro flow cell in accordance with claim 13, wherein said
first spacer includes a slot extending along its length to
accommodate adhesive.
31. A 3D micro flow cell in accordance with claim 13 wherein said
first spacer comprises a photoresist and said second spacer
comprises a printed silicone rubber such that after full
vulcanization said substrates are joined together frictionally,
reversibly, and so as to be fluid tight.
32. A 3D micro flow cell in accordance with claim 13 wherein said
first spacer is photolithographically produced on said lower
substrate and has a width that substantially corresponds to
parallel separation of said first spacer and said second spacer and
wherein said upper substrate is attached to said lower substrate
through adhesive force.
Description
BACKGROUND OF INVENTION
[0001] The invention relates to a method for producing a 3D micro
flow cell, consisting of a lower and an upper substrate between
which is located a flow channel that is penetrated by an electrode
structure connected to external contacts, wherein at least one of
the substrates is equipped initially with a conductive trace and
electrode structure and is provided at the ends of the flow channel
with feedthroughs for connecting a fluid inlet and outlet. The
invention further relates to a 3D micro flow cell produced using
the method.
[0002] 3D micro flow cells of this nature are used, for example, as
cell manipulators for the handling and optical analysis of
dielectric biological particles, in particular of cells and/or
bacteria or viruses. To this end, the micro flow cells are equipped
with a flow channel at the ends of which are provided one or more
fluid inlets and outlets. Said fluid inlets and outlets are made by
feedthroughs extending perpendicular to the flow channel, for
example. The height of the fluid channel is generally in the range
of a few micrometers, while the flow channel is delimited at the
top and bottom by glass substrates and/or silicon substrates and at
the sides by suitable channel walls. In order to be able to hold
individual cells "freely suspended" at a predetermined location
within the fluid channel, electrodes that generate an electrical
field when a voltage is applied are located in the fluid channel.
The electrostatically held cell can then be illuminated by suitable
illumination and observed by means of a microscope.
[0003] A variety of technologies are generally known to make it
possible to implement such three-dimensional structures. Thus, for
example, a glass substrate can be wet chemical etched on one side
in order to produce a flow channel therein and subsequently be
joined by diffusion welding to a second glass substrate as the
cover element. The requisite electrodes for handling cells or
biological particles are previously applied to the first and/or
second glass substrate by known photolithographic methods, and the
second glass substrate is subsequently mounted face down on the
bottom glass substrate.
[0004] However, the technology of diffusion welding is relatively
expensive and the capabilities of generally isotropic glass
structuring are limited. It can be considered a further
disadvantage that only relatively coarse electrode structures can
be applied to the structured glass surfaces. However, in order to
be able to implement exact handling of individual cells or
biological particles, an extremely precise geometric structure of
the electrodes is necessary to be able to electrostatically
manipulate these particles and hold them in place at the desired
location in a noncontacting manner.
[0005] Another technology is described by
Muiller/Gradl/Howitz/Shirley/Sch- nelle/Fuhr in the journal
"BIOSENSORS & ELECTRONICS," No. 14 (1999), pp. 247-256.
Described here is the application of the purely manual epoxy resin
gluing technique, wherein first a polymer spacer is processed on a
glass surface that has previously been equipped with platinum
electrodes and electrically conductive traces. Then the glass
substrate is coated outside the polymer structure with a synthetic
resin, such as epoxy resin, as an adhesive and after that a second
piece of glass, which likewise has been equipped with electrodes,
is positioned thereupon and the bond is subsequently compressed.
This assembly step is usually performed with a so-called die bonder
(chip bonder).
[0006] There are difficulties here in that it is problematic to
manufacture micro flow cells that always have exactly identical
geometric dimensions and in which it is certain that no adhesive
penetrates into the flow channel during the assembly process,
something which would partially narrow the channel. The efficiency
of this step is thus extremely poor and unsuitable for mass
production.
[0007] Moreover, a so-called underfill technique has become known
in which a first polymer (thick lacquer) is spun onto the glass
substrate that is equipped with electrodes, wherein the thickness
of the spun-on polymer is predetermined by the height of the
channel provided. The positive channel system is then structured
from this polymer, i.e. the excess thick lacquer is completely
removed during this photostructuring. The second glass substrate is
then aligned with and pressed onto the first glass substrate. The
3D arrangement obtained in this manner is held by lateral
penetration of a creepable adhesive (underfiller), a second
polymer, after which the channel system in the first polymer is
washed out again with a solvent. The solvent must not attack the
second polymer here. A particular disadvantage here is that no
inner flow elements can be manufactured in the channel in this way
because they cannot be reached by the second polymer. Moreover,
this technique is extremely time-consuming and limited with respect
to structural resolution.
[0008] The object of the invention is to disclose a method for
producing a 3D micro flow cell that can be implemented economically
and with which especially uniform geometric parameters can be
achieved. The invention further has the object of creating a 3D
micro flow cell that can be produced economically with the method
according to the invention.
SUMMARY OF THE INVENTION
[0009] The object of the invention is achieved with regard to a
method for producing a 3D micro flow cell consisting of a lower and
an upper substrate between which is located a flow channel that is
penetrated by an electrode structure connected to external
contacts, wherein at least one of the substrates is equipped
initially with a conductive trace and electrode structure, and is
provided at the ends of the flow channel with feedthroughs for
connecting fluid inlets and outlets. A first spacer provided
defining both sides of the channel, and additional spacing shims
consisting of a substantially non-compressible or curable material
of a predetermined depth, are applied at least to the lower
substrate, and irreversibly fixed to the lower or upper substrate
once applied. A pasty adhesive is applied with a uniform thickness
as a second spacer outside of the flow channel, and in that the
upper substrate is subsequently positioned on the lower substrate
and joined thereto by the action of force and heat, thus
simultaneously sealing the flow channel.
[0010] This simple to implement method ensures extreme precision of
the geometric dimensions of the flow channel on the one hand, and
full and simple sealing of the channel on the other hand, without
the risk of amounts of adhesive penetrating the flow channel, which
could narrow it.
[0011] In a first refinement of the invention, the second spacer is
applied directly next to the first spacer, parallel to and
surrounding it, wherein the thickness of the second spacer prior to
assembly is greater than the height of the first spacer.
[0012] In a special variant of the invention, the first spacer is
provided with a groove running along it, and the pasty second
spacer is dispensed or printed in the groove. As a result of this
version, penetration of adhesive (second spacer) into the flow
channel when the upper substrate is placed on the lower substrate
and during the subsequent compression is reliably prevented.
Moreover, even relatively large spacer heights can be achieved
without problem.
[0013] The shallow groove can be produced with the usual
photolithographic means.
[0014] There are various possibilities for producing the first
spacer and the shims. Thus, the first spacer and the distance
pieces can be applied to the lower substrate by screen printing or
dispensing and subsequently cured, with the curing accomplished by
the action of heat or by irradiation with light or UV, for
example.
[0015] Another possibility consists in that the first spacer and
the shims are produced on the lower substrate by means of a
photolithographic method and then cured through tempering. To this
end, preferably the first spacer and the shims are made of a
photostructurable resist, wherein the remaining thickness defines
the height of the flow channel. Photolithographic methods permit
reduced edge roughness as compared to screen printing, and thus
greater precision, so that finer structures can be produced.
[0016] Another possibility consists in that the first spacer and
the shims are made of a prestructured metal or polymer film that is
adhesive at least on one side and affixed to the lower
substrate.
[0017] An adhesive based on epoxy resin or silicone rubber is
preferably used as the second spacer to fasten the upper substrate
to the lower substrate, i.e. to produce the 3D structure. The bond
between the upper and lower substrate can be produced under the
action of pressure and heat and/or light or UV irradiation.
[0018] The object of the invention is further attained by a 3D
micro flow cell consisting of a lower and an upper substrate
wherein located between the substrates is a flow channel that is
provided with fluidic feedthroughs and is penetrated by an
electrode structure connected to external contacts, characterized
in that arranged at least on the one substrate are a first spacer
defining the flow channel, and additional shims consisting of a
substantially non-compressible or curable material of a
predetermined thickness, that are irreversibly fixed to one of the
substrates, and in that the other substrate is joined to the first
substrate, tightly sealing the flow channel, by means of a pasty,
curable adhesive layer forming a second spacer.
[0019] In a first embodiment of the invention, the second spacer
extends outside the flow channel on both sides on the outer side of
the first spacer, parallel to and surrounding the latter.
[0020] In a second embodiment of the invention, a shallow groove
for accommodating a pasty second spacer is incorporated in the
surface of the first spacer, by which means the penetration of
adhesive into the flow channel during the process of assembling the
upper substrate onto the lower substrate is reliably prevented.
[0021] The thickness of the first spacer and the shims must be
equal and should be between 10 .mu.m and 1 mm, depending on the
intended height of the flow channel.
[0022] In a refinement of the invention, at least one of the two
glass substrates can have a thickness from 250 .mu.m to 1000 .mu.m
and the other can be from 500 .mu.m to 1000 .mu.m thick. In this
way, the composite possesses sufficient mechanical stability and at
the same time is suitable for use in high resolution
microscopy.
[0023] The upper substrate can also consist of a plastic film, for
example a polymer film, with a thickness from 170 .mu.m to 200
.mu.m.
[0024] Another embodiment of the invention is characterized in that
the region of the flow channel is optically transparent at least in
the wavelength range from 250 nm to 450 nm. This can be achieved
simply through the selection of suitable materials for the upper
and lower substrates.
[0025] In another special embodiment, the invention is
characterized in that at least one of the upper or the lower
substrates has metallic microelectrodes that stand in a
predetermined three-dimensional geometrical relationship to one
another and in that the upper substrate is mounted face down on the
lower substrate. The microelectrodes of the upper substrate are
equipped with contact pads and are electrically connected to the
external contacts on the lower substrate by conductive adhesive,
conductive rubber, or solder pads.
[0026] The microelectrodes can consist of a thin film system, of
platinum, gold, tantalum, titanium, aluminum, or a conductive ITO
(indium tin oxide).
[0027] In a special embodiment of the invention, the electrode and
connection system on the upper and lower substrates is insulated
over its entire area by means of an inorganic insulating material,
where the insulating material is omitted in the interior of the
flow channel, on the contact pads, and on the contact supports in
order to permit adequate electrical contact at these locations.
[0028] In order to mask fluorescence of the polymer of the first
spacer--which forms the flow channel--resulting from light
excitation during optical microscopic detection, an opaque mask may
be applied to the outside of the upper substrate in such a manner
that at least the edge region of the flow channel is covered, but
its central region is left clear. The particular advantage of such
a mask is that fluorescence-based detection of biological cells in
the flow channel can take place without the possibility of the
fluorescence that is simultaneously produced by the materials that
delimit the flow channel exerting a disruptive influence.
[0029] The mask can advantageously also be designed as internal and
external shielding for electromagnetic and bioelectric waves, thus
reliably preventing any incident electromagnetic radiation from
exerting a negative effect on the cells themselves and thus on the
result of the detection.
[0030] In the simplest case, the mask consists of metal, which can
also consist of a photolithographically structurable thin film, for
example of Cu or Al.
[0031] It is useful for the thin film to be removable so that the
entire width of the flow channel can be optically examined when
needed.
[0032] In a special refinement of the invention, in order to
prevent the formation of an adhesive film on the inside of the flow
channel insofar as possible, the contact surface of the first
spacer is provided with a slot or other type of recess extending
along its length to accommodate adhesive during the assembly
process.
[0033] In special cases, it can be desirable for the upper
substrate to be removably bonded to the lower substrate. For this
case, a special variant of the invention is characterized in that
the first spacer consists of a photoresist and the second spacer of
a printed silicone rubber, and after full vulcanization, the upper
and lower substrates are joined together frictionally, reversibly,
and so as to be fluid tight. In this way, the 3D micro flow cell
can be opened again after use and sterilized when needed.
[0034] Another special variant of the invention is characterized in
that the first spacer is photolithographically produced on the
lower substrate and has a width that substantially corresponds to
the parallel separation of first spacer and second spacer and in
that the upper substrate is attached to the lower substrate through
adhesive force. However, this variant of the invention is only
suitable for cases in which the upper substrate does not contain an
electrode structure.
[0035] The invention is explained in detail below with an exemplary
embodiment.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] FIG. 1 is a schematic top view of a 3D micro flow cell.
[0037] FIG. 2 shows a sequence of manufacture of the lower
substrate of the 3D micro flow cell.
[0038] FIG. 3 shows the assembly sequence for completion of the 3D
micro flow cell.
[0039] FIG. 4 is a sectional view of FIG. 3 the 3D micro flow cell
as a glass/glass module.
[0040] FIG. 5 is a sectional view of a 3D micro flow cell with flip
chip contacts.
[0041] FIG. 6 shows a 3D micro flow cell equipped with a Cu
mask.
DESCRIPTION OF THE INVENTION
[0042] Seen in FIG. 1 is a 3D micro flow cell in accordance with
the invention that consists of a lower substrate 1 made of glass
with a thickness of approximately 750 .mu.m and an upper substrate
2. In the present case, the upper substrate is likewise made of
glass with a thickness of approximately 150 .mu.m, although other
materials that have adequate transparency in the wavelength range
from 250-450 nm can also be used here. Located between the two
substrates 1 and 2 is a flow channel 3 that is provided at each end
with a fluidic feedthrough 4 for inlet and outlet of a fluid. The
flow channel 3 is delimited laterally over its entire length by a
first spacer 5 and an additional second spacer 6, which extends
outside the flow channel 3 on both sides next to the first
spacer.
[0043] Moreover, an electrode structure 7 that is connected to
external contacts 9 via conductive traces 8 is located on the upper
substrate 2 and the lower substrate 1.
[0044] In contrast to the conductive traces 8 on the lower
substrate 1, the conductive traces 8 on the upper substrate 2 end
in contact pads 10, which are electrically connected to the
external contacts 9 on the lower substrate 1 by means of conductive
adhesive or solder pads or micro solder balls (micro balls) 18
(FIG. 5).
[0045] In addition, all external contacts 9 on the lower substrate
1 are combined in a contact support 11 whose purpose is additional
mutual insulation.
[0046] To electrostatically hold cells 12 or biological particles
or the like at a predetermined location within the flow channel 3
(cf. FIG. 5), the electrode structure 7 contains microelectrodes
13, which extend into the flow channel on the lower substrate 1 or
the upper substrate 2 as applicable, and are exactly positioned in
three dimensions.
[0047] Spacing shims 14 are also provided, moreover, in order to
achieve a spacer distance between the substrates 1, 2 that is
constant over the substrate.
[0048] In order to better illustrate the design of the individual
structures on the lower substrate 1, FIG. 2 shows a suitable
sequence. To this end, the lower glass substrate 1 is first bored
in order to be able to later implement the necessary fluidic
feedthroughs 4 to the flow channel 3. The lower substrate 1 is then
provided with the electrode structure 7 and the conductive traces 8
as well as the external contacts 9 by means of conventional thin
film techniques and photolithography. The entire structure is then
insulated over its entire surface with an inorganic insulating
material 15 (FIG. 5). The insulator 15 is then removed in the
region of the future flow channel 3 and at the external contacts 9
in order to be able to produce effective electrical structures.
[0049] Subsequently, the flow channel 3 is formed on the lower
substrate 1 in that a first spacer 5 made of a polymer, is applied
to the lower substrate 1. Of course, the first spacer can
alternately be formed on the upper substrate 2. A high-viscosity
positive photoresist, a negative dry resist, or a polymer film
applied by screen printing can be used to produce the first spacer
5. All three variants allow the manufacture of a first spacer 5
that can have a thickness in the range of 10 .mu.m to 100 .mu.m. It
is important in each case that the thickness of the spacer 5 also
determines the height of the flow channel 3.
[0050] Next, the first spacer 5 is cured through the action of heat
or UV radiation. It is extremely important in this step that after
curing, the first spacer 5 has the precise thickness that the flow
channel 3 should later have.
[0051] After that, the second spacer 6, surrounding the first
spacer 5, is applied to the lower substrate 1 by printing or with
the use of a dispenser. The thickness of the second spacer 6 is
greater than that of the first spacer 5. An adhesive based on epoxy
resin or silicone rubber is used as the second spacer 6 in any
event.
[0052] It is also possible to form in the surface of the first
spacer a shallow groove 19 (FIG. 6) running along it using known
photolithographic methods and to dispense or print the second
spacer (adhesive) therein. The depth of the groove is between 10-35
.mu.m.
[0053] The upper and lower substrates 1, 2 are then glued in an
aligned position.
[0054] The advantage of this variant is that sandwich systems with
significantly greater spacer heights over 20-50 .mu.m can also be
implemented.
[0055] For the upper substrate 2 shown in FIG. 3a, only an
electrode structure 7 is produced in the same manner as on the
lower substrate and is connected to contact pads 10 via conductive
traces. This structure as well is subsequently insulated over its
entire surface with an organic or inorganic insulating material 15,
with the electrode structure 7 in the region of the future flow
channel and the contact pads 10 being subsequently exposed again by
removal of the insulating material 15.
[0056] Flip chip assembly takes place next as shown in FIG. 3, in
that the upper substrate 2 is positioned face down exactly over the
lower substrate and is then placed on it. Heat is supplied at the
same time to cure the second spacer 6 and thus create the 3D
structure shown in FIGS. 1, 4, and 5.
[0057] In order to be able to produce the necessary electrical
contacts between the contact pads 10 on the upper substrate and the
external contacts 9 on the lower substrate, a suitable conductive
adhesive 16 is dispensed on the connections prior to flip chip
assembly.
[0058] To prevent adhesive from penetrating the flow channel 3
during the assembly process, there can be incorporated in the
surface of the first spacer 5, a slot or groove, 19 which may be
V-shaped, extending along the length of the same. This can be done
without difficulty using known methods of photolithography.
Moreover, a higher strength of the overall structure is achieved in
this way.
[0059] Since the channel walls of the first spacer 5 generate a
disruptive fluorescence when a cell 12 that is spatially held in
place in the flow channel 3 is illuminated during optical
detection, suitable masking of the fluorescence of the spacer
material is helpful place for high-resolution optical detection,
for example using an immersion objective of a microscope.
[0060] In order to preclude such interference, an opaque mask 17 as
shown in FIG. 6 can be provided that covers the edge of the flow
channel 3 and leaves the central region of the flow channel clear.
Mask 17 can be made of a metallic structurable and aligned thin
film. In order to make such a mask reversible if needed, the use of
an easily removable layer system is beneficial so that the entire
cross-section of the flow channel 3 can be observed as needed.
[0061] The particular advantage of a mask 17 is that
fluorescence-based detection of biological cells 12 in the flow
channel 3 can take place without the possibility of the
fluorescence that is simultaneously produced by the materials that
delimit the flow channel 3 exerting a disruptive influence brought
about by scattered light. It can be considered a further advantage
that, as a result of the mask 17, it is no longer necessary to
provide an additional mask in the optical system, which results in
higher light intensity of the optical system.
[0062] The mask 17 can advantageously also be designed as internal
and external shielding for electromagnetic and bioelectric
radiation, thus reliably preventing normally present
electromagnetic interference from exerting a negative effect on
detection of the cells.
[0063] In the simplest case, the mask 17 can be made of a metal,
where the mask 17 can also consist of a photolithographically
structurable thin film, for example of Cu, Al or another metal.
[0064] In this way, the mask 17 can be removed simply through
etching without harming the micro flow cell.
[0065] In the event that only optical shielding by the mask 17 is
important, the mask can of course be manufactured of other
materials, for example a plastic.
[0066] In special cases, it can be desirable for the upper
substrate 1 to be removably joined to the lower substrate 2. For
this case, a special variant of the invention is characterized in
that the second spacer 6 of silicone rubber is imprinted on the
first spacer 5, and after full vulcanization the upper and lower
substrates 2, 1 are joined together frictionally. The frictional
connection can be implemented with a simple clamping
arrangement.
[0067] In the simplest case, i.e. when the upper substrate contains
no electrode structure 7, a substantial simplification of the
structure of the 3D micro flow cell can be achieved if the first
spacer 5 that has been photolithographically produced on the lower
substrate 1 has a width that substantially corresponds to the
parallel separation of first spacer 5 and second spacer 6 (FIG. 5),
wherein the upper substrate 2 is attached to the lower substrate 1
merely through adhesive force. A prequisite here is that the
contact surface of the first space 5 must be completely even with
the upper substrate.
[0068] While there have been described what are believed to be the
preferred embodiments of the present invention, those skilled in
the art will recognize that other and further changes and
modifications may be made thereto without departing from the spirit
of the invention, and it is intended to claim all such changes and
modifications that fall within the truse scope of the
invention.
* * * * *